The invention relates to an image forming apparatus that includes a first image forming section, a second image forming section, a paper feeding section for feeding paper to each of the first and second image forming sections, and a paper output section for outputting paper on which an image is formed in each of the first and second sections.
As a type of electrophotographic image forming apparatus, a color image forming apparatus is known that is provided with a single image forming section that has toner of four colors, i.e., three subtractive primary colors and black, stored therein and performs both black-and-white and color image forming processes. In a color image forming process, this apparatus superimposes toner images of up to four colors and transfers the superimposed images to paper. In order to obtain a high-quality color image without any out-of-register colors, there is a limit to speed of image forming process. Thus, the color image forming apparatus provided with the single image forming section cannot fully satisfy consumer needs for faster black-and-white image forming processes.
JP H10-086455A discloses an image forming apparatus provided with two image forming sections. A second one of the image forming sections is provided to take over an image forming process in the event of failure of a first one of the image forming sections during the image forming process.
In this arrangement, as an example, the first image forming section may be used for black-and-white image formation, and the second image forming section for color image formation.
However, no conventional apparatus including the one disclosed in JP H10-086455A has a plurality of image forming sections, a paper feeding section, and a paper output section, arranged so as to form a shortest paper transport path.
In the apparatus as disclosed in JP H10-086455A, a paper transport path leading from the second image forming section to the paper output section is formed in such a manner as to detour paper around the first image forming section provided nearer to the paper output section. The bend in the transport path for paper on which an image is formed in the second image forming section to be transported on is likely to cause paper to be jammed or damaged.
Thus, the conventional apparatus cannot provide both of fast black-and-white image forming processes and high-quality color image forming processes. This problem also occurs in an image forming apparatus, of other type than an electrophotographic image forming apparatus, such as an inkjet image forming apparatus, that is provided with a plurality of image forming sections.
A feature of the invention is to provide an image forming apparatus that has a plurality of image forming sections, a paper feeding section, and a paper output section, arranged in such a manner as to render paper transport paths as simple as possible, thereby enabling both fast black-and-white image formation and high-quality color image formation.